Miniature fuse

Abstract

A miniature cartridge-type fuse comprises a sub-assembly of an inner insulating housing made of a transparent glass or glass-like material which cannot withstand the forces of a short circuit overload, and end cap terminals at the ends of the housing. A transparent encapsulating body is preferably molded immovably around the inner housing and covers, seals and physically interconnects the exposed exterior surfaces of the inner housing and terminals. The encapsulating body prevents the hazardous destruction of the fuse under all overload conditions and enables the fuse element to be seen through the encapsulation body and inner housing.

I claim: 
     
       1. A miniature cartridge fuse having a length no more than about one quarter inch, and an outer diameter no greater than about 0.1 inch, said fuse comprising: a subassembly of an inner transparent insulating housing which cannot withstand short circuit blowout conditions, a fuse element disposed within said inner housing and a pair of conductive terminals at the opposite axial ends of said housing electrically and physically connected to the ends of said fuse element; said sub-assembly being encapsulated by an outer transparent encapsulating body of insulating material immediately surrounding the exterior surfaces of said inner housing to reinforce it for substantially its entire extent, and said encapsulating body being made of transparent material to enable the fuse element to be seen through and the surrounding encapsulation material, and is a much stronger material than the material out of which said inner housing is made and to prevent the explosion of the fuse under fuse blowout conditions. 
     
     
       2. The cartridge fuse of claim 1 wherein said inner housing is made of glass and said encapsulation body is a molded transparent synthetic plastic material. 
     
     
       3. The cartridge fuse of claim 2 wherein said inner housing is an open ended body, and said terminal means being cupshaped end caps telescoping over the ends of said housing and anchored thereto by solder within the housing. 
     
     
       4. The cartridge fuse of claim 3 or 2 wherein said fuse has a rated current of at least about 15 amps. 
     
     
       5. The cartridge fuse of claim 3 or 2 wherein there are conductive leads extending from said terminals, said encapsulating body surrounding and sealed around said leads. 
     
     
       6. The cartridge of claim 2, 3 or 4 wherein there are conductive leads extending from said terminals, said encapsulating body surround and sealed around said leads, said inner housing is an open ended body, and said terminals are cup-shaped end caps telescoping over the ends of said housing and anchored thereto by solder within the housing, said leads extending outwardly of said terminals and said encapsulating body is molded around said inner housing, terminals and inner portions of said leads.